The present invention relates to testing data packet transceivers, and in particular, to testing wide band data packet signal transceivers using narrow band test equipment.
Many of today's electronic devices use wireless technologies for both connectivity and communications purposes. Because wireless devices transmit and receive electromagnetic energy, and because two or more wireless devices have the potential of interfering with the operations of one another by virtue of their signal frequencies and power spectral densities, these devices and their wireless technologies must adhere to various wireless technology standard specifications.
When deciding such wireless devices, engineers take extra care to ensure that such devices will meet or exceed each of their included wireless technology prescribed standard-based specifications. Furthermore, when these devices are later being manufactured in quantity, they are tested to ensure that manufacturing defects will not cause improper operation, including their adherence to the included wireless technology standard-based specifications.
For testing these devices following their manufacture and assembly, current wireless device test systems employ a subsystem for analyzing signals received from each device. Such subsystems typically include at least a vector signal generator (VSG) for providing the source signals to be transmitted to the device under test, and a vector signal analyzer (VSA) for analyzing signals produced by the device under test. The production of test signals by the VSG and signal analysis performed by the VSA are generally programmable so as to allow each to be used for testing a variety of devices for adherence to a variety of wireless technology standards with differing frequency ranges, bandwidths and signal modulation characteristics.
As part of the manufacturing of wireless communication devices, one significant component of production cost is costs associated with manufacturing tests. Typically, there is a direct correlation between the cost of test and the sophistication of the test equipment required to perform the test. Thus, innovations that can preserve test accuracy while minimizing equipment costs (e.g., increasing costs due to increasing sophistication of necessary test equipment, or testers) are important and can provide significant costs savings, particularly in view of the large numbers of such devices being manufactured and tested.
For example, the commonly known and widely used wireless standard known as “WiFi” is the result of a succession of standards and for which the signal bandwidth has grown to include orthogonal frequency division multiplex (OFDM) signals up to 160 megahertz (MHz) wide (e.g., IEEE 802.11 ac standard). However, test equipment designed to test compliance with WiFi standards are in most cases limited to signal bandwidths of 80 MHz or less. Thus, such a tester is not adequate for testing a WiFi signal whose bandwidth exceeds 80 MHz. Accordingly, this would preclude testing IEEE802.11ac standard signals of 160 MHz. Increasing the capability of this test equipment to support measurements of 160 MHz wide signals would increase its cost. And, since few test points exist within these 160 MHz wide signal channels, such significant cost increases for the test equipment would yield little benefit in terms of additional testing capability.
Further, wireless devices designed for the IEEE 802.11ac standard are also capable of operating under the IEEE 801.11n standard with signal bandwidths of 40 MHz or less. Thus, a single tester applied to testing such a device would be capable of testing the IEEE 802.11n standard signals but would not be able to test the 160 MHz wide IEEE 802.11 ac standard signal. Instead, the required tester would need to be capable of capturing and analyzing signals of 160 MHz or more. The cost of such test systems is considerably higher than that of current testers capable of testing 80 MHz wide signals, and can result in unnecessary redundancy, since much of the baseband processing engines can be shared between the narrower and wider radio frequency (RF) signal paths. Further, many more test points exist for 20, 40 and 80 MHz wide signal channels, as compared to the 160 MHz wide signal channels. Accordingly, the acquisition costs of a tester capable of testing both IEEE 802.11n and 802.11ac signals up through the full 160 MHz wide frequency band is greater, thereby affecting the overall cost of manufacturing test for such advanced wireless devices.
Accordingly, it would be desirable to have a technique for testing increasingly sophisticated DUTs without necessarily requiring increasingly sophisticated testers.